
import javax.swing.JPanel;

/**
 * @(#) ArraowLinePanel.java
 *
 * Copyright 2004 Opensource Develop Team. All rights reserved.
 */

// package
// import classes
import java.awt.*;
import java.awt.geom.Area;
import java.awt.geom.GeneralPath;
import java.awt.geom.Line2D;

/**
 * 在Panel上画一个箭头
 *
 * @author ODT
 * @version 1.0 22/04/2004
 * @see JPanel
 * @since 1.3
 */
class ArrowLinePanel extends JPanel
{
     // confirm the line position
     Line2D line = new Line2D.Float(100f, 100f, 300f, 300f); 

     ArrowLinePanel()
     {
     setBackground(Color.white);
     }

     public void paintComponent(Graphics g)
     {
           super.paintComponent(g);

           Graphics2D g2D = (Graphics2D) g;
           g2D.setColor(Color.red);
           g2D.draw(line); // draw line without arrow.

           double x1 = line.getX1();
           double x2 = line.getX2();
           double y1 = line.getY1();
           double y2 = line.getY2();
           // compute the line's length
           double length = Math.sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2)); 
           g2D.translate(x1, y1); 
           // compute the angle between line and X axis.
           double roate = Math.atan((y2-y1)/(x2-x1)); 
           // draw arrow
           GeneralPath path = new GeneralPath();
           path.moveTo((float)length, 0);
           path.lineTo((float)length - 10, -5);
           path.lineTo((float)length - 7, 0);
           path.lineTo((float)length - 10, 5);
           path.lineTo((float)length, 0);
           path.closePath();

           Area area = new Area(path);
           g2D.fill(area);
     }
}